This invention relates generally to high frequency transmission lines and more particularly to planar type waveguide structures for millimeter wave applications.
Guided wave transmission lines are widely used to channel the flow of high-frequency electrical energy. Common examples of these transmission lines are the coaxial line, the hollow metallic waveguide and the optical fiber. All these waveguiding structures are useful in long link applications. However, in situations where the distance between the transmitting and receiving points is below a few inches, as in an integrated circuit, planar transmission lines offer an attractive alternative to these types of transmission lines. A variety of planar transmission line configurations are possible.
In one type of planar transmission line, metallic conductors play a primary role in the waveguiding process. This includes the well known microstrip transmission line, the slotline, the coplanar waveguide, and coplanar strip line. In another type of planar transmission line, a dielectric strip plays a primary role in the waveguiding process. This includes the well known dielectric strip guide and the inverted strip guide, typical examples of which are respectively disclosed in U.S. Pat. No. 4,028,643, entitled "Waveguide Having Strip Dielectric Structure", which issued to T. Itoh on June 7, 1977 and U.S. Pat. No. 4,463,330, entitled "Dielectric Waveguide" which issued to T. Yoneyama on July 31, 1984.
In general, all of these offer significant savings in size and weight over the non-planar varieties. Further, monolithic and hybrid technologies are closely compatible with the planar configuration. Consequently, these technologies can be used to generate with higher producibility, systems which offer superior performance and enhanced reliability. When combined with high-volume batch fabrication, significant cost savings can result.